A computer implemented method to improve security in authentication/authorization systems and computer programs products thereof

ABSTRACT

A computer implemented method and computer program products to improve security in authentication/authorization systems 
     The computer implemented method comprising controlling the access to different resources and actions defined for a user by a first server, reducing the exposure time at which such operations are available, establishing a dual channel verification through the use of a second server and a defining a secure channel for certificate exchange for authentication. 
     The computer programs implement the method.

FIELD OF THE ART

The present invention is directed, in general, to authentication and authorization systems. In particular, the invention relates to a computer implemented method and computer program products to improve security in authentication/authorization systems in which the access to different resources and actions defined for a given user are controlled.

BACKGROUND OF THE INVENTION

In recent years, web fraud detection market has increased considerably, so innovation in authentication and authorization processes has become of great importance.

The increasing complexity of applications has led to the adoption of many security techniques increasingly sophisticated. One of the classifications that can be proposed for the study of these security techniques allows distinguishing between authentication solutions and authorization solutions. The authentication techniques are designed to verify a person is the one who claims to be. In order to add more reliability in verifying that actually a person corresponds to the identity that is being checked, many alternative authentication schemes can be taken or the number of factors to build this authentication can be extended.

There are many solutions designed to strengthen the authentication processes and, by extension, to fortify the authorization processes. Once users have been securely identified, there are authorization schemes that allow flexibility and robustness in assigning permissions to users to ensure secure access to system resources. However, there are threats which cannot yet be thwarted by adopting any of the existing schemes for the authentication/authorization, or this adoption is too expensive to afford it. These threats directly affect the way the access to specific resources is performed. A method to address these threats involves the designing of brand new security mechanisms. These mechanisms must guarantee that once the identity of a user has been verified and the level of authorization to a resource for this user has been checked, the actions taken by the user of that resource are not intercepted and modified by any attacker.

In any authorization model different techniques that facilitate access to various system resources are included. The user role information, the access control data provided when the user is authenticated, are examples of information that can be used to determine whom to give access to what resources and how this access has to be guaranteed. Ultimately, determining what should be accessed by the users, will be specified for each application. For this reason, sometimes it will be difficult to provide a general authorization scheme. It will be necessary to define an application-specific logic to determine what users can access and how they would perform these accesses. From this idea, there are many solutions that propose secure and flexible schemes for the implementation of the authorization. In all these solutions, the security must be guaranteed by the correct selection of the authentication mechanism and a correct implementation of the selected authorization scheme.

Some of the solutions provide flexibility by defining their own SDK to encourage the use of their schemes for authentication/authorization. Today, most of the SDK are based on concepts introduced by OAuth and do not suppose a risk by themselves. This applies to Microsoft Live Connect, Facebook PHP SDK and Windows 8 SDK Authentication Broker. If they exist, the threats should come from a deficient use of these SDK. In fact, regardless of threats derived by a poor implementation of the scheme chosen, most of the threats that can be defined on an authorization system coincide with the threats defined for authentication systems. This coincidence has to do with the misuse of the credentials used to manage permissions granting access to resources [2], [5].

In [2] four different levels are defined in terms of the consequences of authentication and authorization errors and misuse of credentials. Level 1 is the lowest level (the most insecure) and level 4 is the highest.

-   -   Level 1—An attacker can perform repeated logon trials by         guessing possible values of the token authenticator. An attacker         is also able to replay previously captured messages (between a         legitimate user and a verifier) to authenticate as that user to         the verifier. NIST recommends the usage of a single or         multi-factor authentication with no identity proof in order to         provide protection against these online guessing and replay         attacks.     -   Level 2—An attacker can listen passively to the authentication         protocol to capture information which can be used in a         subsequent active attack to masquerade as the user. NIST         recommends the usage of single or multi-factor authentication to         provide protection against these eavesdropping attacks and all         the attacks from the level 1.     -   Level 3—The attacker positions himself or herself in between the         user and verifier so that he or she can intercept and alter the         content of the authentication protocol messages. The attacker         typically impersonates the verifier to the user and         simultaneously impersonates the user to the verifier. Conducting         an active exchange with both parties simultaneously may allow         the attacker to use authentication messages sent by one         legitimate party to successfully authenticate to the other. NIST         recommends the usage of a multi-factor authentication and wide         use of OTP. It also suggests a token used for authentication to         be unlocked by the user using a password or biometrics. Adopting         these solutions provides protection against verifier         impersonation attacks, MitM attacks and the attacks from level         2.     -   Level 4—An attacker is able to insert himself or herself between         a user and a verifier subsequent to a successful authentication         exchange between the latter two parties. The attacker is able to         pose as a user to the verifier, or vice versa, to control         session data exchange. On the other hand, the attacker may         compromise or otherwise exploit authentication tokens and may         intercept all input or output communications from the device         (Man-in-the-device (MitD) attacks or Man-in-the-Browser (MitB)         attacks). The attacker can do this infecting the system with         malware. NIST suggests the usage of Multi-factor authentication         with FIPS-140-2 certified tamper-resistant hardware (hardware         tokens) [4] to get protection against these session hijacking         attacks and the attacks from the level 3.

For the first three levels, attacks and existing solutions are both focused on the way of verifying the user's identity. At level 4, NIST proposes the use of solutions against session hijacking and others attacks over authentication processes. This session hijacking involves an attacker takes advantage of the legitimate exchange of credentials that a user makes to comply with the authentication process. Once this validation is accomplished, the attacker then intervenes in the communication that takes place. This type of attack can be implemented in two ways: actively acting, hijacking the connection and leaving out of it to the legitimate user, or, remaining hidden and modifying the content of communication transparently to the user. Whatever the implementation of this attack, it is important to observe that this is an attack aimed at breaking the authorization system, leaving intact, though useless, the authentication system. Although there are alternatives to proactively protect systems from this threat, there is no adequate solution to mitigate the effects of the attack once the device from which the resource access is requested, is committed.

NIST suggests employing FIPS-140-2 certified tamper-resistant hardware (hardware tokens) [4]. Using these devices provides the users the ability to generate a single use password (one time password, OTP) to prove their identity to each transaction. In addition, there are hardware implementations of these tokens that can generate other OTPs coded to contain information on how to complete a specific transaction.

Different criteria can be defined to establish comparison between authentication/authorization schemes. In [1] the authors suggest the need to define three criteria in order to perform an effective comparison. These aspects are: security, usability and complexity on implementation (deployability). This paper presents an intensive study to instrument the comparison through the definition of metrics.

Following table summarizes the metrics defined for each criterion.

Usability Memory-Effortless Scalable-for-Users Nothing-to-Carry Physical-Effortless Easy-to-Learn Efficient-to-Use Infrequent-Errors Easy-recovery-from-Loss Deployability Accessible Negligible-Cost-per-User Server-Compatible Browser-Compatible Mature Non-Proprietary Security Resilient-to-Physical-Observation Resilient-to-Targeted-Impersonation Resilient-to-Throttled-Guessing Resilient-to-Unthrottled-Guessing Resilient-to-Internal-Observation Resilient-to-Leaks-from-Other-Verifiers Resilient-to-Phishing Resilient-to-Theft No-Trusted-third-Party Requiring-Explicit-Consent Unlikable

In the case of security criterion, the proposed metric set summarizes all the aspects that are usually estimated in defining a threat model. In the definition of these models it is necessary to adopt a number of decisions. And these decisions define the working scenario. For example in the case of OAuth 2.0 [5] the adopted assumptions are as follows:

-   -   The attacker has full access to the network between the client         and authorization servers and the client and the resource         server, respectively. The attacker may eavesdrop on any         communications between those parties. He is not assumed to have         access to communication between the authorization server and         resource server.     -   An attacker has unlimited resources to organize an attack.     -   Two of the three parties involved in the OAuth protocol may         collude to mount an attack against the third party. For example,         the client and authorization server may be under control of an         attacker and collude to trick a user to gain access to         resources.

Attending to the metrics introduced above, is possible to determine that solutions corresponding to the higher security level (level 4) have poor performance in deployability and usability. Once the assessment of a system allows to determine in which level has to be deployed its authentication system, it is needed to evaluate if the users are authenticated safely and correctly. Although there are some tools that aid in this task [3], [6], deploys in the level 4 are difficult to evaluate correctly. In terms of usability, the use of tampering resistant hardware tokens goes against the adoption of these solutions by users, and it has been proved that this situation leads to a misuse of the credential systems. These tokens are expensive. They are independent devices that the user has to custody and that can be employed with one service provider only. If the users have to deal with more than one service provider that has adopted these tampering resistant hardware tokens, they have to take into custody as many tokens as service providers they have.

Furthermore, in terms of authorization, in [7] the authors explain that, aside from some security issues of each SDK, developers who choose to integrate with one of them make assumptions that can lead to security problems. This is because SDKs are often not well documented and the security exploits nearly always stem from attackers who find ways to violate these assumptions system implementers relied upon.

Along with these difficulties, other problems must be considered to understand the constant increase in fraud arising from the theft of digital identities. For instance, it is not possible to measure a homogeneous security level in all users' digital accounts. It is needed a solution that can equalize the security level of all digital accounts that a user owns. This solution should extend this security not only to the authentication processes but also to the resource authorization processes and all procedures related to such accounts.

Apart from problems derived from the authorization solutions adoption, the most extended solution for authentication, the usage of personal digital certificates, has also many problems that usually have led to a very poor adoption in most systems, especially when they have to provide services to a wide number of clients. For instance, by the user side some of these problems are:

-   -   Valid digital certificate possession. Not all users have to have         a valid digital certificate. And, in addition, this certificate         may not be used in processes related to authentication. This         problem is solved if there is a government program aimed at         issuing digital certificates with the identity of its citizens         (citizen cards, etc. . . . )     -   Digital certificate storage by users. These certificates can be         stored in the computer, but this solution limits its use to a         single machine. By other hand, they can also be stored on a         smartcard. In this case, the limitation to a single computer is         beaten to reach all those computers that have a compatible         smartcard reader.     -   Latency. The processes associated with the implementations of         the authentication mechanisms cause always an overhead over the         time to authenticate a user.     -   Secure environment to execute cryptographic procedures over         these digital certificates.

By the service provider side, the problems rise according with the cost of maintaining a Public Key Infrastructure (PKI) infrastructure that always add complexity to the system functionality. However, regardless of these problems, the use of the certificates to authenticate a user is a very robust process that normally involves two steps. First, the issuer entity must associate a user identity with a public key in a safe way. Secondly, a mechanism that allows exploiting the use of cryptographic protocols to verify a user's identity has to be proposed. These two phases should be performed independently using trustable channels.

When the use of these digital certificates is employed to certify the identity of a user computing mobile device there are three different possibilities to store the private information of the certificate and to perform securely the corresponding cryptographic processes: use a pure-software solution to store the private key and let the microprocessor of the computing device perform the cryptographic procedures; use a hardware container (e.g. the SIM of a mobile phone) to securely store and execute the cryptographic procedures without using the computation resources provided by the computing device; or employ a smart-card technology that relies on an external device to store and execute the cryptographic procedures, forcing to design and implement a compatible port to access this device.

Therefore, a different approach is needed to improve the overall security in the authentication/authorization systems, whatever is the scheme or schemes adopted, minimizing the impact on the usability and deployability of these systems.

REFERENCES

-   -   [1] Bonneau, J., Herley, C., van Oorschot, P. C., & Stajano, F.         (2012, May). The quest to replace passwords: A framework for         comparative evaluation of web authentication schemes. In         Security and Privacy (SP), 2012 IEEE Symposium on (pp. 553-567).         IEEE.     -   [2] Burr, W. E., Dodson, D. F., & Polk, W. T. (2006). Electronic         authentication guideline. NIST Special Publication, 800, 63.     -   [3] Dalton, M., Kozyrakis, C., and Zeldovich, N., Nemesis:         Preventing Authentication & Access Control Vulnerabilities in         Web Application, In Proceedings of the 18th conference on USENIX         security symposium, (pp. 267-282) USENIX Association.     -   [4] Evans, D., Bond, P., Bement, A., Security Requirements for         Cryptographic Modules, FIPS PUB 140-2—FEDERAL INFORMATION         PROCESSING STANDARDS PUBLICATION. Online Resource:         http://csrc.nist.gov/publications/fips/fips140-2/fips1402.pdf     -   [5] McGloin M. & Hunt P. (2013, January) OAuth 2.0 Threat Model         and Security Considerations. ISSN: 2070-1721. Online resource:         http://tools.ietf.org/pdf/rfc6819.pdf.     -   [6] Sun, F., Xu, L., & SU,Z. (2011,August) Static detection of         Access control vulnerability in web applications. In Proceedings         of the 20^(th) USENIX conference on Security (pp. 11-11).         USENIX.     -   [7] Wang, R., Zhou, Y., Chen, S., Qadeer, S., Evans, D., &         Gurevich, Y. (2013). Explicating SDKs: Uncovering Assumptions         Underlying Secure Authentication and Authorization (Vol. 37).         Microsoft Research Technical Report MSR-TR-2013.

DESCRIPTION OF THE INVENTION

To achieve the above, the invention provides in a first aspect a computer implemented method to improve security in authentication/authorization systems, which comprises: receiving, a first server, from a user having a computing device, a request to be logged into a service of said first server; and authenticating, said first server, credentials information of said user in order to authorize said service request.

In a characteristic manner and on contrary of the known proposals, the computer implemented method of the first aspect further comprises the use of a second server, in connection with said user computing device that has installed therein a dedicated program, for receiving from the first server a first request about a status associated to said user in order to assist the first server in authorizing or rejecting the requested service logging, and in case said requested service logging being authorized, and a request is done by the user to perform an operation in the first server, the second server receiving from the first server a second request about a status that the user has set for said operation and evaluating said operation status to check if the first server being allowed to access the user configuration for said operation. In case the recovered operation status is set as valid, an extra authentication factor mechanism for reinforcing said operation is used, said extra authentication factor mechanism including the use of a public/private key encryption process or the use of a public/private key for generating a digital signature.

In accordance with the invention, the first request performed by the first server comprises: a credential exchange between the first server and the second server in order to provide mutual authentication; verification, by the second server, of said associated status of the user, said associated status been previously set as valid or as invalid by said user and stored in a memory of the second server; and the sending, by the second server, of the associated status of the user to the first server.

The credentials exchange to secure mutual authentication between the first server and the second server, is performed, preferably, via a standard authentication procedure based on certificates' exchange defining, as a result, a secured channel. The exchange is performed to verify that both first server and second server are who they claim to be.

The second server may notify the user in case said request to be logged into a service of the first server is rejected. For instance, by the sending of a Short Message Service (SMS), of an email, of or a message by a smartphone messenger application, or just by the highlighting or pushing in said dedicated program of said user computing device.

The associated status is set as valid (unlocked) or as invalid (locked) a certain period of time and can be modifiable by the user whenever the latter want it. For instance, the user can plan a locking/unlocking policy to automate the management of their accounts held with different servers using different criteria: time, geolocation (different policies for home, work, etc.). Another possibility for modifying said associated status can be by delegating the control said user has of their accounts to other users. This can be done by considering two different options. In the first one, a parental control mechanism is used so the children's (original) accounts access control is delegated to the parent control mechanism. In the second one, a single account allows multiple locks. In this latter case, the unlock action will require that multiple users unlock their locks concurrently. In both cases, the delegation is performed securely maintaining the privacy of every user unchanged.

In addition, the request to be logged into a service and/or the request to perform an operation may be recorded in order to provide statistics. In this way, the user can obtain system usage statistics that reflect activity of the system and track the attempts of impersonation. These statistics inform about when someone had attempted to access to a service with user's username.

In accordance with an embodiment, the solution previously proposed to provide the extra authentication factor mechanism is extended with the use of a public/private key for generating a digital signature by means of: generating and sending, the second server to the dedicated program, a one-time password (OTP) that the user is going to use for setting up the extra authentication factor mechanism; recovering, the dedicated program, a private key of the user in order to digitally sign the received OTP, said recovering been performed after the user having decided to sign the received OTP within the dedicated program and having stored said private key in a software or a hardware mechanism of the computing device; and sending, the dedicated program, the digitally signed OTP to the second server and the digital signature employed, the latter verifying integrity of the received digitally signed OTP with the OTP that the second server generated, and integrity of the private key that was used to perform said signing of the OTP with an stored user public key that the second server (200) had.

In addition, if the private key used to perform the signing of the OTP matches the user public key stored in the second server, the second server sends to the first server the result of said operation status request, performed by the first server, along with the generated OTP; then, the first server request the OTP to the user, the latter recovering the OTP through the dedicated program that further sends it to the first server; finally, the first server checks if the OTP received from the second server and the OTP received from the user matches.

In accordance with another embodiment, the solution proposed to provide the extra authentication factor mechanism is extended by the usage of a public/private key encryption process. This is achieved by means of performing, after having sent the second server the result of said operation status request to the first server including an OTP used by the user for setting up the extra authentication factor mechanism, the following actions: requesting, the first server to the user through an interface, said OTP used by the user for setting up the extra authentication factor mechanism; encrypting, the second server, the OTP with a public key of the user and sending the encrypted OTP to the dedicated program, said public key been previously stored in the second server by the user; recovering, the dedicated program, a private key of the user and using the private key of the user to decrypt the received encrypted OTP, said recovering been performed after the user having stored the private key in a software or a hardware mechanism of the computing device; sending, the dedicated program, the decrypted OTP to the user, the latter sending the decrypted OTP via said interface; and checking, the first server, if the OTP received from the user and the OTP received from second server matches.

In accordance with another embodiment, the solution proposed to provide the extra authentication factor mechanism is extended with the use of a public/private key encryption process. The public/private key encryption process is performed by the first server by means of executing, after the second server having sent the result of said operation status request to the first server, the following actions: first generates an OTP that the user is going to use for setting up the extra authentication factor mechanism; then encrypts the generated OTP with a public key of the user and further sends the encrypted OTP to the second server, said public key been previously stored in the first server by the user; and after that requests to the user through an interface, the OTP; at that time the second server sends the encrypted OTP to the dedicated program which recovers a private key of the user and uses the private key of the user to decrypt the received encrypted OTP, said recovering been performed after the user having stored the private key in a software or a hardware mechanism of the computing device; finally the dedicated program sends the decrypted OTP to the user that sends the decrypted OTP via said interface to the first server, so that the first server can check if the OTP received from the user and its own generated OTP matches.

The requesting of the OTP to the user and the sending of the encrypted OTP to the dedicated program in this embodiment are preferably performed at the same time.

In accordance with yet another embodiment, the solution proposed to provide the extra authentication factor mechanism is extended with the usage of a public/private key for generating a digital signature by means of performing, after the second server having sent the result of said operation status request to the first server, the following actions: first, the first server generates an OTP that the user is going to use for setting up the extra authentication factor mechanism and sends the generated OTP to the second server; after that, the first server requests the user through an interface the OTP and the second server sends the OTP to the dedicated program; the dedicated program then recovers a private key of the user in order to digitally sign the received OTP, said recovering been performed after the user having decided to sign the received OTP within the dedicated program and having stored said private key in a software or a hardware mechanism of the computing device, and sends the digitally signed OTP and the digital signature employed for the signing to the second server which forwards the received information to the first server; preferably, at the same time of the sending of the digitally signed OTP and the digital signature employed for the signing to the second server, the dedicated program also sends the digitally signed OTP to the user that can then send to the first server the digitally signed OTP via said interface; finally, the first server checks if the digitally signed OTP received from the user and the digitally signed OTP received from the second server matches.

The subject matter described herein can be implemented in software in combination with hardware and/or firmware, or a suitable combination of them. For example, the subject matter described herein can be implemented in software executed by a processor.

According to a second aspect there is provided a computer program comprising computer program code means adapted to perform the steps according to the computer implemented method of the first aspect of the invention when said program is run on a computer, a digital signal processor, a field-programmable gate array, an application-specific integrated circuit, a micro-processor, a micro-controller, or any other form of programmable hardware.

Embodiments of the invention also comprise a computer program product including program code means adapted to perform other embodiments of the invention according to the methods of claim 3, 4, 5, 6 or 8.

The present invention allows the user to plan a locking/unlocking policy to automate the management of accounts held with different servers using different criteria: time, geo-localization (different policies for home, work, etc.); delegate the control of their accounts to other said second server users; enable monitoring systems that allow users to be warned of identity theft attempts or untrue user's impersonation in operation execution requests, providing a course of action to take action to control the digital identity; establish a second factor for authentication for verifiers that are not providing it; establish an account to be blocked or unblocked and change it with immediate effect by the use of a switch control; fix a schedule to Valid/Invalid (unlocked/locked) an account or said operation automatically based on time and date settings. Once a check-status request is received the second server responds based on the current state of the scheduler; improve the security level of an account or said operation by configuring a second factor authentication integrated with second server; control different actions associated with an account, authorizing or banning the execution of them in a compatible manner with the authorization scheme established.

Furthermore, the invention allows homogenizing the security level for all the different accounts a user has. It allows offering a security level comparable with level 4 defined by NIST. And this is done for different accounts that can be now controlled with only one device and regardless of the authentication/authorization scheme defined for every service provider.

The invention does not propose any new authentication/authorization scheme. Indeed, the intention is to complement the existent schemes with an extra security layer. Although this may limit its usability and deployability, the invention design is oriented to minimize the impact over these criteria. As it is stated before, the authentication scheme choice determinates the security risk that is assumed for an authorization system. What is proposed here is to reduce the risk taken with the choice of any authentication/authorization mechanism reducing the time in which this system is accessible to be broken.

Assuming that there is a relationship between the success and failure of an attack on the auth system with the time in which this system is accessible (exposure time) as conditional probability (p (SuccessfulAttack I exposed)) is possible determining that the relative risk (RR) satisfies the following expression:

$\begin{matrix} {{RR} = {\frac{p\left( {{SuccessfulAttack}{exposed}} \right)}{p\left( {{SuccessfulAttack}{unexposed}} \right)} > 1}} & {{Eq}.\mspace{14mu} 1} \end{matrix}$

In this expression it is assumed that the probability of success of an attack is directly related to the exposure time. That is, the continuous exposure of a computer system, in this case the authentication system, increases the likelihood of success of an attack in contrast with a scenario in which the exposure is limited. In the same way one can evaluate the following expression:

$\begin{matrix} {\frac{\frac{p\left( {{successfulAttack}{exposed}} \right)}{p\left( {{FailedAttack}{exposed}} \right)}}{\frac{p\left( {{SuccessfulAttack}{{un}{exposed}}} \right)}{p\left( {{FailedAttack}{unexposed}} \right)}} > 1} & {{Eq}.\mspace{14mu} 2} \end{matrix}$

Indicating that there is a greater probability for a successful attack if exists a continued systems exposure. It is also possible to estimate the portion of all successful attacks that could have been avoided if the exposure had been avoided (Attributable Risk Percent (ARP)). This is calculated with expression 3.

$\begin{matrix} {{ARP} = \frac{{RR} - 1}{RR}} & {{Eq}.\mspace{14mu} 3} \end{matrix}$

This expression allows assessing the investment required to enable a solution designed to reduce the time that is accessible authentication process. The professional experience and technical knowledge of the documented attack techniques to break authentication/authorization systems confirm the assumption made earlier (RR>1).

This reduction in the exposure time allows mitigating the effects of most of the threats related with the authentication phase before a user can access to some privileged resources. This invention also permits reducing the exposure of particular actions that can be taken after the login process has been accomplished. Therefore, this exposure reduction supposes the limitation in the time in what the action can be executed and the establishment of a channel that allow to send critical information to assure the integrity of this action execution.

The invention encompasses the solutions for the threats defined by NIST. But, in this case, these solutions are provided to users through a dedicated program designed to be executed in a mobile device, which facilitates the interaction with a second server. In addition, this second server brings privacy in the communications relative to the control of the user's accounts and incorporates all the control information that the users have set about the actions the service providers have offered them.

BRIEF DESCRIPTION OF THE DRAWINGS

The previous and other advantages and features will be more deeply understood from the following detailed description of embodiments, with reference to the attached, which must be considered in an illustrative and non-limiting manner, in which:

FIG. 1 is an illustration of the present invention general architecture.

FIG. 2 is a flow diagram illustrating an account pairing sequence with authorization.

FIG. 3 is a flow diagram illustrating how a status of a user account can be checked for authentication.

FIG. 4 illustrates the embodiment in which the accuracy of the extra authentication factor solution for a service provider that does not implement a PKI is increased based on a public/private key encryption process.

FIG. 5 illustrates the embodiment in which the accuracy of the extra authentication factor solution for a service provider that does not implement a PKI is increased based on digital cryptographic signature.

FIG. 6 illustrates the embodiment in which the accuracy of the extra authentication factor solution for a service provider that implements a PKI is increased based on a public/private key encryption process.

FIG. 7 illustrates the embodiment in which the accuracy of the extra authentication factor solution for a service provider that implements a PKI is increased based on digital cryptographic signature.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

In reference to FIG. 1 it is showed the general architecture of the present invention. Concerning FIG. 1, a user computing device 100 such as a mobile phone, a smartphone, a tablet-PC or a PDA among any other, is used by said user in order to login into a dedicated program 102 in communication with a second server 200 and to manage the status for every first server 300 with which a user wants to request a service.

With this new proposal said user 100 can unblock said operation defined for a particular account created with said first server 300. As stated below, this action can enhance the control defined for this account by decision of the first server 300. In this decision, the first server 300 can choose to incorporate a new control of security beyond the block/unblock default option or second authentication factor mechanism. This control of security consists of to provide a communication channel from the user 100 to the first server 300, through the second server 200. The first server 300 can configure the system to ask the user 100 for a particular information related to said operation to be performed. This information can be used by the second server 200 to verify if the user 100 is who actually is demanding said operation and to confirm if the operation that has arrived to the first server 300 is exactly as the one the user 100 had ordered.

Assuming that the first server 300 could want to verify the integrity of the operation, it can be selected what parameters are critical to ensure the operation integrity. In this case, it is important that the requested information corresponds univocally with the operation critical parameter in order to identify it correctly.

In this architecture, the user 100, besides having an account in the second server 200, can have multiple accounts with different service providers. One of these service providers is the first server 300. Once the user 100 completes the login process with these accounts he or she will have access to multiple operations specific to each service providers. The second server 200 eases how a first server 300 can integrate this control within the logic of its applications.

When a first server 300 decides to integrate its services, it will provide the ability to link their accounts with the accounts that the user 100 has in the second server 200. When the user 100 decides to establish this link, she or he starts a pairing process that ensures complete privacy to the user 100. Once the pairing process is completed, the user 100 can access the configuration of the control of the account with the first server 300 from a dedicated program 102 (i.e. a mobile application).

Every time the settings associated with an account are changed on said mobile application or dedicated program 102, this modification is immediately propagated to the second server 200 to change the status of the account that can be accessed by the first server 300.

Second server core implements the main function of the second server 200: lock or unlock said user account with the first server 300 and the operations provided by first server 300. In order to do that, the second server 200 accepts and processes the check-status requests sent from the first server 300. This second server 200 also manages all data about the links with said first server 300 defined by the user 100 and the requests for the pairing of new locks. The key is the user 100 is never asked for any private information. Once the user 100 creates his account with second server 200, he can establish locks with different service providers, like said first server 300. To activate these locks the second server 200, according to an embodiment, generates a token. A unique token and the definition of secured channels are needed to complete the pairing process between the user 100 and the first server 300. As result of this pairing process, the cryptographic token is sent from the second server 200 to the first server 300 who has to store this information with their user's personal data. Later, this cryptographic token will be used to request the corresponding lock status. The user 100 can modify the status of their locks, by the activation or configuration of the different options that second server 200 provides.

In case the user 100 has set up a lock with a second (or extra) authentication factor mechanism over an account or a particular action, the second server 200 will incorporate all the needed logic for the generation and communication of the OTP. When the second server 200 receives a request from the first server 300 asking for the user account status, a second authentication factor is triggered. An OTP is generated and sent to the user 100. The same OTP is sent to the first server 300 along with the account status. If the status is ON and the user 100 has activated the second factor, the first server 300 should prompt the user to introduce the OTP to proceed with the operation.

Now, if the user 100 has set up a lock over a said operation with an integrity factor to verify that the operation parameters have not been modified, said second server 200 incorporates the needed logic to get the critical information from the user 100 and from the first server 300 and to check if both are equal. The second server 200 sends the result of the checking as the account status to the first server 300. In case of mismatching, the first server 300 can conclude that an intruder can be intercepting the information from the user 100. The first server 300 can then build mechanisms to elude the fraud and to raise security alerts.

In reference to FIG. 2 it is illustrated a pairing process of the user 100 account of the second server 200 with different accounts for different first servers 300. In FIG. 2, once a user 100, using for instance the dedicated program 101 such as a browser, has completed the login process (A-B) with a first server 300 (in this particular case a Bank online, a social network, a credit card providers, etc.), the user 100 decides to perform said accounts' pairing process. The user 100 requests the pairing to the first server 300 (C) using the browser 101. As response, the first server 300 asks for a pairing token (D). The user 100 then uses the dedicated program 102 (D′) to get this pairing token from the second server 200, after a previous login process. The second server 200 generates a token (for instance as an OTP) (E) and sends it to the user's dedicated program 102 (F). This token can be used for several pairing processes meanwhile it is valid. The user get the token (OTP) from the dedicated program 102 and introduces it in the web page displayed in the browser 101 by the first server 300 (G-G′). The first server 300 then sends the received token to the second server 200, after a previous credentials exchange (H). If the first server 300 identity is validated, the second server 200 stores the link between the user 100 and the first server 300 and generates a new token that identifies this link. This token (accountID) is sent to the first server 300 (I) and there it is stored for future communications (J). At last, a pairing acknowledges is sent to the user's browser 101 (K).

In reference now to FIG. 3 it is illustrated how a status of a user account can be checked for authentication. In FIG. 3, a user 100, using for example a browser 101, requests to be logged in a service (A) of a first server 300 so once user existence has been validated (B) by said first server 300, the latter demands to the second server 200 the user account status (C). Then the second server 200 initializes the credentials exchange before the result of the account status information is sent (D). With the result status, the first server 300 makes the decision of allowing or blocking the user access (E).

In an embodiment, if the account status is unlocked or valid but the second authentication factor is on, within the answer of the status request, the second server 200 sends an OTP to the first server 300 that has to employ to complete the authentication. The first server 300 then requests to the user 100 the OTP that is going to be a temporal second factor (F). Then the second server 200 sends the same OTP to the to the user's dedicated program 102 (G). The user 100 recovers the OTP from the dedicated program 102 and introduces it in the browser 101 (H) and sends it to the first server 300 (I). The first server 300 can check if the OTP sent through the browser 101 matches with the one received with the account status (J). Depending on of the results of this verification, the first server performs the authentication process (K) and communicates the result to the user via 101.

When a first server 300 sends a Status Request, the second server 200 understands that someone, with the proper service identification information (i.e. ID and password), is trying to access to the service. If the account status is set as blocked, or if this request has come in a moment that is not included in the interval defined by the user 100, the second server 200 registers this event as a fake attempt. The second server 200 could send, according to an embodiment, an alert of this event to the user if said user has configured it so (for instance by sending a Short Message Service (SMS), an email, a message by a smartphone messenger application, by a highlighting or pushing in said dedicated program 102 of said user computing device 100, etc.) or just update the statistics for a later revision. Then the second server 200 returns the status associated with the account as locked.

With the aim of improving the security of any authentication/authorization system, the use of the said second server 200 is proposed as a new layer that gives the users the chance of control the access to the resources and procedures associated with their accounts defined with any first servers. These resources and procedures are seen as operations which depend on the main actions defined for an account (i.e. login process). This dependency is established like a hierarchy where the changes in the root entries are propagated to their children.

Moreover, a secure channel for certificate exchange in order to improve authentication is also proposed. Therefore, instead of having to configure a process to verify the usage of a digital certificate by legitimate user (e.g. configuration of a smartcard reader) for each of the computers from which access is desired, said user just has to use the dedicated program 102 in communication with the second server 200 to do it. Two different scenarios are proposed: first, it is considered a scenario in which the first server 300 is unable or has decided not to implement a Public Key Infrastructure (PKI) within its organization. In this case, the present invention not only provides a solution to unify the interfaces that the user 100 has to employ to introduce her/his private key and operate with it. In addition, it releases the first server 300 from the responsibility of implement and support a PKI. The second scenario proposed gives response for those service providers that do not want to rely on a third party to manage their PKI.

FIG. 4 illustrates an embodiment in which the accuracy of the extra authentication factor mechanism is increased based on a public/private key encryption process to demonstrate that the user, who is demanding an operation, has one of the next alternatives: a private key of a digital certificate, an specific computing mobile device with a private/public system built-in or a physical token that provides all the necessary to perform cryptographic procedures in a secure way (e.g. smartcard used as citizen card). The extra authentication factor mechanism assures that the user who is demanding the execution of a particular operation is, also, in possession of the legitimate user's credentials to access to the second server 200.

Therefore, once the user 100 has requested an operation (A) and has exchanged the credentials that authenticate her/him for the first server 300 (B), the first server 300 determines which ID allows to identify this operation for this user 100 (C) to the second server 200 and performs an operation status request to said second server 200 to retrieve the status that the legitimate user 100 has set, through the second server 200 (D), for said operation. Then, the second server 200 checks if the first server 300 is allowed to access to the configuration that the user 100 has established to the particular operation and recover the status (E) that can be on or off. This information can, also, indicate if the corresponding operation is reinforced with said extra authentication factor. In this embodiment, this extra authentication factor is, in addition, hardened with the usage of a digital certificate. So, based on encryption, it validates that the user 100, who is in possession of the credentials with the second server 200 and who knows the private key of the legitimate user, can provide them at the moment when the operation is requested.

At that time, the second server 200 sends the information related with the status to the first server 300 (F), where it has been included the token used as OTP. While the first server 300 requests the OTP to the user 100 (G), the second server 200 uses the public key information previously stored by the user 100 to encrypt the OTP (H) and sends it to the user's dedicated program 102 (I). Within the device, and depending of the alternative chosen to store the user's private key (a pure-software solution, a hardware container or a smart-card technology) and operate with it, the solution retrieves this private key (J), decrypts the OTP (K) and allows the user 100 to enter it in the interface that the first server 300 has employed for demand this token (L). Once this token has been sent to the first server 300 (M), it is possible to determine if it matches with the token received from the second server 200 (N). If both tokens are the same, then the first server 300 can assume that the user who is demanding an operation could correspond with the user, who has decrypted the OTP, has sent it and, consequently, is in possession of the private key of the digital certificate stored by the second server 200.

FIG. 5 illustrates an embodiment in which the accuracy of the extra authentication factor solution is increased by the usage of a public/private key to digitally sign an authentication token to show that the user 100 who is demanding an operation is in possession of the private key of a certificate, an specific mobile device with the private information built inside or a physical token guarding this private information (e.g. smartcard used as citizen card). Therefore, in this embodiment, the first server 300 is absolved from the responsibility of incorporating or supporting any public key infrastructure.

Once the user 100 has requested an operation (A) and has exchanged the credentials that authenticate her/him for said first server 300 (B), the first server 300 determines which ID allows to identify this operation for this user 100 (C) to said second server 200 and performs an status request to the second server to retrieve the status that the legitimate user has set, through the second server 200 (D), for said operation. The second server 200 checks if the first server 300 is allowed to access to the configuration that the user 100 has established to the particular operation and recover the status (E) that can be on or off. This information can, also, indicate if the corresponding operation is reinforced with the extra authentication factor. In this embodiment, this extra authentication factor is, in addition, hardened with the usage of a digital certificate. So, based on a digital signature mechanism, it validates that the user 100, who is in possession of the credentials with the second server 200 and who knows the private key of the legitimate user, can provide them at the moment when the operation is requested.

Therefore, and in difference with other embodiments, before sending the operation status to the first server 300, an exchange of information is initialized if the second server 200 detects that said operation is configured with the extra authentication factor reinforced with digital signature. First, the first server 300 generates and sends an OTP as token for this extra factor mechanism to the dedicated program 102 (F). With this OTP, if it is needed, some information about the operation can be attached. This way, the user can decide sign or not sign the OTP received taking into consideration this information. If the user 100 has decided to sign, within the computing device and depending of the alternative chosen to store the user's private key and operate with it, the solution retrieves this private key (G), compute the signature for this OTP (H) and it re-sends the OTP along with the signature to the second server 200 (I). Then the second server 200 verifies if the OTP is the same that was sent (J) and verifies, also, the signature (K). For this verification, the second server 200 previously must have stored the legitimate user's public key. If it is a valid signature then the second server 200 sends the status to the first server 300 (L). Along with the status information, the same OTP used to authenticate the user 100 is sent to the first server 300. In fact, this is an OTP verified. So, when the first server 300 requests the OTP to the user 100 (M) and verifies that the user 100 sends the same OTP (O and P), at least, it can be sure that the user 100 who requests the operation is in possession of the legitimate user's credentials for the second server 200 and that this user 100 also custodies the private key of the digital certificate. If the signature received by the second server 200 is not valid, then the second server 200 returns an OFF status for the operation (Q) and the first server 300 could decide to deny its execution (R).

FIG. 6 illustrates an embodiment in which the accuracy of the extra authentication factor mechanism is increased based on a public/private key encryption process to demonstrate that the user who is demanding an operation is in possession of the private key of a certificate, an specific computing mobile device with a private/public system built-in or a physical token that provides all the necessary to perform cryptographic procedures in a secure way (e.g. smartcard used as citizen card). In this case, the solution is provided in view of the fact that the first server 300 assumes the responsibility of incorporating or supporting a public key infrastructure.

Once the user 100 has requested an operation (A) and has exchanged the credentials that authenticate her/him for the first server (B) 300, the first server 300 determines which ID allows to identify this operation for this user (C) to the second server 200 and performs an status request to the said second server to retrieve the status that the legitimate user has set, through the second server 200 (D), for said operation. The second server 200 checks if the first server 300 is allowed to access to the configuration that the user 100 has established to the particular operation and recover the status (E) that can be on or off. This information can, also, indicate if the corresponding operation is reinforced with the extra authentication factor. In this embodiment, this extra authentication factor is, in addition, hardened with the usage of a digital certificate. So, based on encryption, it validates that the user 100, who is in possession of the credentials with the second server 200 and who knows the private key of the legitimate user 100, can provide them—credentials and private key—at the moment when the operation is requested.

The second server 200 then sends the information related with the status to the first server 300 (F), but, in difference with other embodiments, now the OTP is not generated by the second server 200. Instead of that, it is the first server 300 which generates it and, using user's public key information, previously stored, encrypts it (G) and sends it to the second server 200 (H). Here the second server 200 plays the role of secure channel just making easy and secure the exchange of information. So, while the first server 300 requests the OTP to the user 100 (J), the second server 200 sends the encrypted OTP to the dedicated program 102 (I). The dedicated program 102 receives the ciphered information and, depending of the alternative chosen to store the user's private key and operate with it, the solution retrieves this private key (K), decrypts the OTP (L) and allows the user 100 to enter it in the interface that the first server 300 have employed for demand this token (M). Once this token has been sent to the first server 300 (N), it is possible to determine if it matches with the token received from the second server 200 (O). If both tokens are the same, then the first server 300 can assume that the user 100 who is demanding an operation could correspond with the user 100 who has decrypted the OTP, has sent it and, consequently, is in possession of the private key of the digital certificate stored by the first server 300.

FIG. 7 illustrates an embodiment in which the accuracy of the extra authentication factor mechanism is increased by the usage of a public/private key to digitally sign an authentication token to show that the user 100 who is demanding an operation is in possession of the private key of a certificate, an specific computing mobile device with the private information built inside or a physical token guarding this private information (e.g. smartcard used as citizen card). In this case, the solution is provided in view of the fact that the first server 300 assumes the responsibility of incorporating or supporting a public key infrastructure.

Once the user 100 has requested an operation (A) and has exchanged the credentials that authenticate her/him for the first server 300 (B), the first server 300 determines which ID allows to identify this operation for this user 100 (C) to said second server 200 and performs an operation status request to the second server 200 to retrieve the status that the legitimate user has set, through the said seconds server 200 (D), for the said operation. The second server 200 checks if the said first server 300 is allowed to access to the configuration that the user 100 has established to the particular operation and recover the status (E) that can be on or off. This information can, also, indicates if the corresponding operation is reinforced with an extra authentication factor. In this embodiment, this extra authentication factor is, in addition, hardened with the usage of a digital certificate. So, based on cryptographic digital signature, it validates that the user 100, who is in possession of the credentials with the second server 200 and who knows the private key of the legitimate user 100, can provide them at the moment when the operation is requested.

The second server 200 then sends the information related with the status to the first server 300 (G), but, in difference with other embodiments, now the OTP is not generated by the second server 200. Instead of that, it is the first server 300 which generates the OTP (H) and sends it to the second server 200 (I). Here the second server 200 plays the role of “out of band” channel just making easy and secure the exchange of information. So, while the first server 300 requests the OTP to the user 100 (J), the second server 200 sends the OTP to the said dedicated program 102 (K). The dedicated program 102 receives the information and, depending of the alternative chosen to store the user's private key and operate with it, the solution retrieves this private key (L), digitally signs the OTP (M) and sends both, the OTP and the signature to the second server 200 (N).Then it allows the user 100 to enter the OTP in the interface that 300 have employed for demand this token (O). Once this token and its signature have been sent to the first server 300 (P), it is possible to determine if it matches with the token received from the second server 200 (Q and R). If both tokens are the same, then the first server 300 can assume that the user 100 who is demanding an operation could correspond with the user 100 who has signed the OTP, has sent it and, consequently, is in possession of the private key of the digital certificate stored by the first server 300.

The proposed method may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium.

Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Any processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

As used herein, computer program products comprising computer-readable media including all forms of computer-readable medium except, to the extent that such media is deemed to be non-statutory, transitory propagating signals.

The scope of the present invention is defined in the following set of claims. 

1-15. (canceled)
 16. A computer implemented method to improve security in authentication/authorization systems, the method comprising: receiving, by a first server, from a user via a first dedicated program, a request to be logged into a service of said first server; and authenticating, by said first server, credentials information of said user in order to authorize said service login request, said credentials information comprising information validating the identity of the user in the first server, the method comprising: receiving, by a second server, from a second dedicated program installed in a computing device of said user, configuration information that the user has established for the operations provided by the first server; requesting, by the user, once the service login request being authorized by the first server, to perform an operation in the first server; receiving, by the second server, from the first server, a request about an operation status associated to what said user has established about said requested operation in order to assist the first server in authorizing or rejecting the requested operation; and verifying, by the second server, said operation status previously established by the user for said requested operation, and in case said operation status being established as valid by the user, the second server generating an extra authentication factor mechanism for reinforcing authorization of said requested operation, wherein said extra authentication factor mechanism includes a public/private key encryption process or the use of a public/private key for generating a digital signature.
 17. The computer implemented method of claim 16, wherein said request performed by the first server to the second server comprises a credential exchange between the first server and the second server in order to provide mutual authentication, and the method comprising the sending, by the second server, of the result of said operation status to the first server.
 18. The computer implemented method of claim 16, wherein said operation been reinforced with the use of said extra authentication factor mechanism including a public/private key for generating a digital signature by means of performing following actions: generating and sending, by the second server to the second dedicated program, a one-time password (OTP) that the user is going to use for setting up the extra authentication factor mechanism; recovering, by the second dedicated program, a private key of the user in order to digitally sign the received OTP, said recovering been performed after the user having decided to sign the received OTP within the second dedicated program and having stored said private key in a software or a hardware mechanism of the computing device; and sending, by the second dedicated program, the digitally signed OTP to the second server and the digital signature employed, the latter verifying integrity of the received digitally signed OTP with the OTP that the second server generated, and integrity of the private key that was used to perform said signing of the OTP with an stored user public key that the second server had.
 19. The computer implemented method of claim 18, further comprising: if the private key used to perform the signing of the OTP matches the user public key stored in the second server, sending, by the second server to the first server, the result of said operation status, performed by the first server, along with the generated OTP; requesting, by the first server, the OTP to the user, the latter recovering the OTP through the second dedicated program and further sending it to the first server; and checking, by the first server, if the OTP received from the second server and the OTP received from the user matches.
 20. The computer implemented method of claim 16, wherein said requested operation been reinforced with the use of said extra authentication factor mechanism including a public/private key encryption process by means of performing, after having sent, by the second server, the result of said operation status to the first server including an OTP used by the user for setting up the extra authentication factor mechanism, the following actions: requesting, by the first server to the user through an interface, said OTP used by the user for setting up the extra authentication factor mechanism; encrypting, by the second server, the OTP with a public key of the user and sending the encrypted OTP to the second dedicated program, said public key been previously stored in the second server by the user; recovering, by the second dedicated program, a private key of the user and using the private key of the user to decrypt the received encrypted OTP, said recovering been performed after the user having stored the private key in a software or a hardware mechanism of the computing device; sending, by the second dedicated program, the decrypted OTP to the user, the latter sending the decrypted OTP via said interface; and checking, by the first server, if the OTP received from the user and the OTP received from second server matches.
 21. The computer implemented method of claim 16, wherein said requested operation been reinforced with the use of said extra authentication factor mechanism including a public/private key encryption process performed by to the first server by means of performing, after the second server having sent the result of said operation status to the first server, the following actions: generating, by the first server, an OTP that the user is going to use for setting up the extra authentication factor mechanism; encrypting, by the first server, the generated OTP with a public key of the user and further sending the encrypted OTP to the second server, said public key been previously stored in the first server by the user; requesting, by the first server to the user through an interface, the OTP; sending, by the second server, the encrypted OTP to the second dedicated program installed in the computing device of the user; recovering, by the second dedicated program, a private key of the user and using the private key of the user to decrypt the received encrypted OTP, said recovering been performed after the user having stored the private key in a software or a hardware mechanism of the computing device; sending, by the second dedicated program, the decrypted OTP to the user, the latter sending the decrypted OTP via said interface; and checking, by the first server, if the OTP received from the user and its own generated OTP matches.
 22. The computer implemented method of claim 21, wherein the requesting of the OTP to the user and the sending of the encrypted OTP to the second dedicated program are performed at the same time.
 23. The computer implemented method of claim 16, wherein said requested operation been reinforced with the use of said extra authentication factor mechanism including a public/private key for generating a digital signature executed by to the first server by means of performing, after the second server having sent the result of said operation status to the first server, the following actions: generating, by the first server, an OTP that the user is going to use for setting up the extra authentication factor mechanism and sending the generated OTP to the second server; requesting, by the first server to the user through an interface, the OTP; sending, by the second server, the OTP to the second dedicated program; recovering, by the second dedicated program, a private key of the user in order to digitally sign the received OTP, said recovering been performed after the user having decided to sign the received OTP within the second dedicated program and having stored said private key in a software or a hardware mechanism of the computing device; sending, by the second dedicated program, the digitally signed OTP and the digital signature employed for the signing to the second server, the latter forwarding them to the first server; sending, by the second dedicated program, the digitally signed OTP to the user, the latter sending the digitally signed OTP via said interface; and checking, by the first server, if the digitally signed OTP received from the user and the digitally signed OTP received from the second server matches.
 24. The computer implemented method of claim 23, wherein the second dedicated program performs both of said sending's, of the digitally signed OTP and the digital signature employed for the signing to the second server and of the digitally signed OTP to the user, at the same time.
 25. The computer implemented method of claim 16, wherein the second server notifies the user if the request to be logged into a service of said first server is rejected.
 26. The computer implemented method of claim 25, wherein said notification comprises one of a sending of a Short Message Service (SMS), a sending of an email, a sending of a message by a smartphone messenger application, a highlighting or pushing in said second dedicated program of said user computing device.
 27. The computer implemented method of claim 16, wherein said operation status is set as valid or as invalid a certain period of time.
 28. The computer implemented method of claim 16, wherein the request to be logged into a service of the first server and/or the request to perform an operation in the first server are recorded in order to provide statistics.
 29. A computer program product, which includes computer program code instructions that when executed in a computer implement the steps of the method of claim
 16. 30. The computer program product of claim 29, further including computer program code instructions that when executed in a computer implement the following: generating and sending, by the second server to the second dedicated program, a one-time password (OTP) that the user is going to use for setting up the extra authentication factor mechanism; recovering, by the second dedicated program, a private key of the user in order to digitally sign the received OTP, said recovering been performed after the user having decided to sign the received OTP within the second dedicated program and having stored said private key in a software or a hardware mechanism of the computing device; and sending, by the second dedicated program, the digitally signed OTP to the second server and the digital signature employed, the latter verifying integrity of the received digitally signed OTP with the OTP that the second server generated, and integrity of the private key that was used to perform said signing of the OTP with an stored user public key that the second server had. 